Remove peel from potatoes and cut into cubes. Clean leek, rinse and cut into pieces (set aside a piece of leek for garnish). Make leek and potatoes in the chicken soup for 20 min. Blend in a hand mixer or possibly with the hand blender.
Whip the cream until stiff, mix with crème fraîche. Fold loosely into the soup. Season to taste with salt, pepper and a pinch of nutmeg.
Cut bread into cubes and toast in a frying pan without fat.
Cut remaining leek into very fine rings. Sprinkle on the soup together with the bread cubes. Serve the soup hot or possibly cooled.